Liquid scintillator for an off-axis neutrino detector? (The Minnesota group) We are actively investigating a liquid scintillator option for the off-axis detector Engineering mostly done (for MINOS) Have made prototypes for test, using PVC extrusions and scintillator from MINOS studies Investigating all aspects of possible optical (CCD) readout schemes – minimizing costs We have all the components to make our own inexpensive ICCD camera

The concept Engineering was done for MINOS Aging, strength of materials, etc. Optical connections, manifolds, etc. Fill method (after installation) Needs  300,000 cells for 20 kT Can we make readout for  $10/cell? Few meters earth, rock… Cells of liquid scintillator  3 cm  3 cm in 15 m (?) long multicell PVC extrusions Every 5 th layer is water

Light yields We achieved best reflectivity of at peak emission (425 nm) Square cell geometry more optimal than MINOS Expected light yield at 15 m in 3 cm ( =10m) =  refl. =  1.33 In 3 cm cells =  1.28 Mirror at end =  1.60  40 photons from 15 m Data from cosmic ray muons crossing a 2.1 cm  2.8 cm PVC extrusion (off-the-shelf – refl. =0.94) 7.5 m from photodetector (HPD, 10% qe); BC517L scintillator 1 mm fiber 3.2 pe average  2.1 cm thick

A possible (likely?) scheme Light emerges from fibers at angles < 47 o (calculated and measured) making lens coupler possible without excessive light loss Fresnel lens has diameter 15 cm, focal length 2.5 cm (3 coupled lenses each with f=7.5 cm) Can get 70% light from WLS at focus for demagnification of ½ - goes down rapidly beyond that

Image intensifier Cheapest from Litton who make zillions for military – “scientific” IIs from Hamamatsu, Photek, Proxitronic, DEP, etc, cost significantly more Generally much quicker delivery compared to “scientific” IIs – take from existing production lines Have bought a Gen-2 (1 MCP) 25 mm diameter (S-20 photocathode, P20 phosphor) - cost was $1990 – should go to $1500 for large quantities We are currently evaluating this device Have measured gain of 0.8  10 4 using light from WLS fiber Must connect to CCD via tapered fiber-optic for maximal light – phosphor light is  isotropic (- taper costs $500 in large quantities!)

CCD CCD quantum efficiency  50%  $500 for Kodak KAF-0401E including components for electronic readout with pixel ganging 6.9 mm  4.6 mm active area (9  m pixels)

CCD read-noise Limiting feature Read-noise a few e/pixel from external amps, etc (- dark current is negligible in our gated operation) We have many pixels/fiber (CCD industry aims for best resolution – we need worst. Solution: Gang pixels together to make bigger pixels – we have electronics to do this – being assembled now

The future We are currently evaluating light amplification/transmission through all components We are assembling CCD electronics Will have an operating ICCD camera in 1 month - see if we can see signal from MINOS scintillators Test liquid scintillator configurations We will study simpler versions – e.g., fibers to manifold block  Fresnel  CCD (no II) We would like help, ideas…….